Variable condenser



Sept. 22, 1931. SHERFY 1,824,629

VARIABLE CONDENSER Filed Sept. 21, 1927 2 Sheets-Sheet l IPOLLAA/DESHE/PFY Sept. 22, 1931.

R. F. SHERFY 1,824,629

VARIABLE CONDENSER Fil-ed Sept. 21, 1927 2 Sheets-Sheet 2 6 i 21/ i I I,4 I [3 in I i I I 2V8 2 INVENTOR.

'fPoLu/vo Esme/err BY I A TTORNEYS.

Patented Sept. 22, 1931 UNITED STATES PATENT OFFICE aonmnn r. snmmr, orwnsmeron, msrnrc'r or cor-emu I VARIABLE connnnsna Application filedSeptember 21, 1927. Serial No. 220,988.

(GRANTED UNDER THE A01 01' IABCII 3, 1883, AS AIENDED AI'BIL 30, 1928;370 0. G. 757) My invention relates broadly to variable condensers andmore particularly to variable condensers for use in high frequency radioapparatus.

The object of my invention is to provide a condenser that is compact insize, accurate in capacity adjustment and free from inherent inductance.

Another object of my invention is to produce a condenser in which thereare no losses occasioned by dead ends.

A further object of my invention is to produce a variable condenser thatis free from the effects of hand capacity when adjustment is required.

Further objects of my invention will appear more fully hereinafter asthe description of the method and apparatus is veloped.

My invention consists substantially in the construction, combination andarrangement of parts associated therewith or as will be more fullyhereinafter set forth as shown by the accompanying drawings and finallypointed out in the appended claims.

Reference is to be had to the accompanying drawings forming a part ofthis specification in which like reference characters indicatecorresponding parts throughout the several views and in which:

Figure 1 is a perspective view of my improved condenser,

igure 2 is a sectional view on XXXX of Figure 1, and

Figure 3 is a modification thereof. Referring to the drawings numeral 1rep resents a base upon which are mounted two upright members 2 and 3.The members 2 and 3 are held firmly in a fixed upright position'by meansof brackets 4 that are secured thereto and to the base 1 by means ofbolts 6.

Between the two upright members are mounted two rolls 6 and 7 ofinsulating material that are rotatable on bearings 7' in the uprightmembers 2 and 3. 'These bearings are so positioned that I tween thecenters of the rolls is that of the diameter of one of the rolls plusthe thickness of the sheets of metal foil 8 and the plane vidual filmsby means of brushes 19 and 20 the distance be- Th upright members.

9 and the thickness of the dielectric rial 10.

The two rolls are rotated together by means of intermeshed gear 11 and12 that are mounted upon the ends of the rolls. The control of therotation of the rolls is accomplished by means of a dial 13 or any othersuitable means which is mounted upon an extension 14 of one of therolls.

Referring particularly to Figure 2 the metal foil 1s wound upon therolls in such a manner that, as the films leave the rolls, the foilsmove in a parallel relation to each other. The inner ends of the filmsare secured to the rolls by the insertion of the end of each in a groove15 in each of the rolls. The outer ends of the films are mechanicallysecured to each other and to the sheet of dielectric material 10 bymeans of clamps 16 and 17 which are held in position by means of bolts18. A portion of the films is cut away around the bolts 18 to preventelectrical contact between the bolts and the films 8 and 9 which wouldproduce a short circuit within the condenser.

Attached to the clam s 16 and 17 and the brackets 4 are strips l a ofresilient material such as elastic rubber, springs or the like thatmaintain the strips of the unrolled films in a vertical position andalso maintain the portions of the films that are wound upon the rolls inimmediate electrical contact with the preceding layers.

Electrical contact is made with the indimate:

that rest firmly against the surface of each film and are in electricalcontact with the terminal blocks 23 and 24 of the condenser.

spring member encased as at 22 has an arm 25 hearing against roller 6 inorder to keepthe rollers 6 and 7 close together at all times.

Figure 3 represents a modification of my invention in which the sheet ofdielectric 10 is firmly fixed in a vertical position between the uprightsupporting members 2 and 3. e mounting is accomplished by means ofbracket plates 4' that are secured to the corners of the dielectricsheet 10 and to the The sheet of dielectric contains a plurality ofperforations 21 through which extend the bolts 18 on the clamp 16. Theseperforations not only permit the movement of the foil along the sides ofthe sheet of the dielectric but also serve as guides for the ends of thefoil. v

Inthe practical construction of the apparatus as shown in Figure 3 inthe modification, I desire to utilize sheets of metal foil made up ofthin sheet brass or other suitable metals of about 1/500ths of an inchthickness. The rolls 6 and 7 and the dielectric material 10 I constructof a resilient insulating material, preferably'rubber, that is capableof contraction and expansion where by the thin foils 8 and 9 can berolled upon rolls 6 and 7 and will remain in parallel relation to eachother at all times due to the flexibility of the material making up therolls, which'compensate for the slight thickness caused in the rollingof the foils.

It should be noted that in either of the types of condenser describedthe use of a dielectric other than air may be eliminated and guidesprovided at the edges of the foils for maintaining them in theirparallel relationship to each other.-

From the description of the apparatus it is to be noted that I haveproduced a condenser that has no losses due to dead ends for by theconstruction shown the rolls of the metallic film constitute merely aterminal for the brushes as the individual turns of the metallic filmsare short circuited. Furthermore I have produced a condenser in whichthere is no hand capacity effect for the reason that any adjustments ofthe capacity of the condenser is made from the sides of the plates ofthe condenser which arrangement reduces the hand capacity effect to aminimum.

It will be understood that the above description and accompanyingdrawings comprehend only the general and preferred embodiment of myinvention and that minor detail changes in the construction andarrangement of parts may be made within the scope of the appended claimswithout sacrificing any of the advantages of my invention.

The invention herein described may be manufactured and used by or forthe Government of the United States for governmental purposes withoutthe payment to me of any royalty thereon or therefor.

Having thus described my invention, what I claim is as follows:

1. In'a variable condenser, a base, supporting members secured thereto,rolls,

metallic films mounted on said rolls and between said members, meanssecuring the free ends of said films together, and means forsimultaneously rolling and unrolling said films in parallel planarrelation to vary the capacity and to form a condenser subsecuring thefree ends of said films to said.

dielectric and means for simultaneously rolling and unrolling said filmson said rolls in parallel planar relation to vary the capacity and toform a condenser substantially planar.

3. In a variable condenser, a base having supporting members securedthereto, rolls mounted for 'rotation between said members, metallic foilhaving one of their ends fastened into said rolls, a dielectric sheetbetween said foils means to maintain the .centers. of said rolls spacedapart a distance substantially that of the diameter of one of said rollsplus the thickness of the foil around said rolls, and the dielectricsheet and means for simultaneously rolling and unrolling said foil onsaid rolls in parallel planar relation to vary the capacity and to forma condenser substantially planar.

4. In avariable condenser, a base having supporting members securedthereto, rolls mounted for rotation between said members, metallic foilshaving one of their ends fastened to each of said rolls and the freeends thereof clamped together, a dielectric sheet between said foilsmeans to maintain the centers of said rolls spaced apart a distancesubstantially the diameter of one of said rolls plus the thickness ofsaid foil around said rolls, and the dielectric sheet and means forsimultaneously rolling and unrolling said foil on said rolls in parallelplanar relation along the faces of the di electric sheet to vary thecapacity and to form "a condenser substantially planar.

5. In a variable condenser a base, supporting members secured thereto,rolls mounted for rotation between said members, metallic foils havingone of their ends fastened to said rolls and the free ends thereofclamped together, a dielectric sheet between said foils and means forsimultaneously rolling and unrolling said foil on said rolls in parallelplanar relation along the faces of the dielectric sheet to vary thecapacity and to form a condenser substantially planar. k

6. In a variable condenser a base, supporting members secured thereto,rolls mounted=for rotation between said members, metallic foils havingone of their ends fastened to said rolls and the free ends thereofclamped together, a dielectric sheet between said foils, means forsimultaneously rolling and unrolling said foil on said rolls in parallelplanar relation along the faces of the dielectric sheet to vary thecapacity and to form a condenser substantially planar, said meanscomprising a gear on each of the rolls, and means for rotating saidgears.

7. In a variable condenser, a base, supporting members secured thereto,rolls mounted for rotation between said members, metallic foils havingone of their ends fastened to said rolls, means securing the free endsof said foils together, a dielectric sheet between said foils, means forsimultaneously rolling and unrolling said foils on said rolls inparallel planar relation to vary the capacity and means for maintainingthe foils in their parallel relation to form a condenser substantiallyplanar.

8, In a variable condenser, a base, supporting members secured thereto,rolls mounted for rotation between said members, metallic foils havingone of their ends fastened to said rolls, means securing the free endsof said foils together, a dielectric sheet between said foils, means forsimultaneously rolling and unrolling said foils on said rolls inparallel planar relation to vary the capacity and means for maintainingthe foils in their parallel relation to form a condenser substantiallyplanar, said means consisting of an elastic element exerting a tensionupon the clamped ends of said foil.

9. In a variable condenser, a base, supporting members secured thereto,rolls mounted for rotation between said members, metallic foils havingone of their ends secured to the rolls, a dielectric sheet between saidfoils, means mechanically clamping the free ends of the foils rigidly ina fixed position relative to each other and insulated from each other bysaid dielectric, means for rolling and unrolling said foil on said rollsin parallel planar relation to each other to vary the capacity of thecondenser, and means for maintaining the foils in their parallelrelation to form a condenser substantially planar Y 10. In a variablecondenser, a base, supporting members secured thereto, rolls, metallicfilms mounted on said rolls and between said members, means securing thefree ends of said fihns together, means for simultaneously rolling andunrolling said films in parallel planar relation to vary the capacityandto form a condenser substan tially planar, and brushes engaging themetallic foils and constituting .the terminals of the condenser.

11. In a variable condenser, a base, supporting members secured thereto,a pair of rolls mounted for rotation between said members, metallicfoils having one of their ends secured to each of said rolls,respectively, a dielectric sheet between said rolls, and meansmechanically clamping the free ends of said foils rigidly in a fixedposition relative to each other and insulated from each other by saiddielectric sheet.

. 12. In a variable condenser, a base, supporting members securedthereto, a pair of rolls mounted for rotation between said members,metallic foils having one of their ends secured to each of said rolls,respectively, a dielectric sheet between said rolls, means mechanicallyclamping the free ends of said foils rigidly in a fixed positionrelative to each other and insulated from each other by said dielectricsheet, and means varyingthe effective area of said foils comprising agear on each roll and means for rotating said gears.

13. In a variable condenser, a base having supporting members securedthereto, rolls mounted for rotation between said members, metallic foilshaving one of their ends secured to each of said rolls, a dielectricsheet between said rolls, means mechanically clamping the free ends ofsaid foils rigidly in a fixed position to each other and insulated fromeach other by said dielectric sheet, means varying the effective area ofsaid foils and means holding said foils in their parallel planarrelation during the variation of the capacity of the condenser to form acondenser substantially lanar.

14. In a variable condenser, a ase having supporting members securedthereto, rolls mounted for rotation between said members, metallic foilshaving one of their ends secured to each of said rolls, a dielectricsheet between said rolls, means -mechanically clamping the free ends ofsaid foils rigidly in a fixed position to each other and in sulated fromeach other by said dielectric sheet, means varying the effective area ofsaid foils, means holding said foils in their parallel planar relationduring the variation of the capacity of the condenser to form acondenser substantially planar and brushes engaging said foils andconstituting the terminal of the condenser.

ROLLAND F. SHERFY.

